Introduction into defect studies in ceramic materials(III) - Positron ...

Defect Chemical Reaction
4. Oxidation and Reduction Reaction.
Oxidation reaction
• Oxidation can be written as the consumption of oxygen vacancies:
1 2
O
2
••
x
( g)
+ V = O + 2h
• For which the equilibrium constant is:
2
p
0 ∆g
KO
= = K exp(
1/
2 O −
••
V P
kT
[ ]
O
O
2
O
• It is important to note that since oxidation and reduction are the
same thermodynamic process simply reversed, the reactions that
we write to describe them are not independent.
• The equilibrium constants in Eqs.2.30 and 2.32 are also not
unitless. Typically, the units will reflect whichever pressure and
concentration units in use.
O
11
•
O
)
( 2.
31)
( 2.
32)